Communication and computing technologies are starting to converge into a single mobile computing device with continuously decreasing form factors. For example, handheld “smart phones” are emerging that combine capabilities such as voice and data communications typically provided by a cellular telephone with application programs typically provided by a computer. Consequently, a mobile user may use a single device to make telephone calls, maintain calendars and contacts, browse the Internet, communicate electronic mail (“e′mail”), and more.
Mobile computing devices such as handheld smart phones include displays. The displays are often liquid crystal display (LCD) types. LCDs create their display by manipulating visible ambient light. In the absence of ambient light, however, the LCD display is difficult to see. Therefore, backlighting is added to make the LCD displays visible in the absence of ambient light. Backlighting modules that are formed either of a single light emitting diode (LED) or an array of LEDs may be used to create the backlight for small and medium LCD displays, such as those used in mobile computing devices. Advantages of using LEDs for backlighting is low cost, long life, immunity to vibration, low operational voltage, and precise control over intensity. The main drawback of LED backlighting is the increased power consumption relative to other techniques. Power consumption is proportional to the size of the LCD display and may become a major drawback for a large LCD display. For small and medium size color LCDs, LED backlighting may be more efficient than other techniques such as CCFL, and the like.
Converting to a more efficient LED in an existing mobile computing device, however, may not be backwards compatible with existing or legacy devices. In addition, modifications to the system hardware or especially to the low level system software of a mobile computing device may require a wireless carrier approval or certification. This process increases device cost and lead time to market to unacceptable levels. A wireless carrier or a mobile telephone operator is a telephone company that provides wireless telephone services for mobile phone subscribers. A wireless carrier generally requires certification of wireless devices deployed or used in their network. Once a wireless device is approved by a wireless carrier, any modifications to the hardware and software in the wireless device platform may require re-approval or re-certification of the modified wireless device. However, the extent of the re-certification effort depends on what is being modified. Generally, if the modifications entail only minor off-platform changes but not changes at the device platform level (i.e., system hardware and especially low level system software), the approval or certification efforts required may be much lower or even may be eliminated.
Therefore, there is a need for techniques to automatically adjust the brightness level for a backlit LCD display independent of the type of backlighting medium being employed without changing the hardware and/or software of a device platform of legacy devices. New devices that use the same display generally will undergo a normal full scale certification process anyway. Therefore, having a new display in the new device case does not create unacceptable burden for the development process. Moreover, if the modifications can be kept minor, it improves predictability of the performance of the new display in both the legacy and new device platform.